Imitator of police officer and unknown jazz fan? (7)
I believe the answer is:
copycat
'imitator' is the definition.
(synonyms)
'police officer and unknown jazz fan?' is the wordplay.
'police officer' becomes 'cop' (cop is a kind of police officer).
'and' means one lot of letters go next to another.
'unknown' becomes 'y' (algebra).
'jazz fan?' becomes 'cat' (slang term for a jazz fan).
'cop'+'y'+'cat'='COPYCAT'
'of' acts as a link.
(Other definitions for copycat that I've seen before include "Person imitating another (or cloned pet?)" , "Person who imitates another in feline way" , "Feline imitator" , "Person imitating others" , "Mimic" .)